/*
 * Copyright 2002-2010 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

using System.Collections;

namespace Spring.Caching;

/// <summary>
/// An abstract <see cref="ICache"/> implementation that can
/// be used as base class for concrete implementations.
/// </summary>
/// <author>Aleksandar Seovic</author>
/// <author>Erich Eichinger</author>
public abstract class AbstractCache : ICache
{
    private bool _enforceTimeToLive = false;
    private TimeSpan _timeToLive = TimeSpan.Zero;

    /// <summary>
    /// Gets/Set the Default time-to-live (TTL) for items inserted into this cache.
    /// Used by <see cref="Insert(object,object)"/>
    /// </summary>
    public TimeSpan TimeToLive
    {
        get { return _timeToLive; }
        set { _timeToLive = value; }
    }

    /// <summary>
    /// Gets/Sets a value, whether the this cache instance's <see cref="TimeToLive"/>
    /// shall be applied to all items, regardless of their individual TTL
    /// when <see cref="Insert(object,object,TimeSpan)"/> is called.
    /// </summary>
    public bool EnforceTimeToLive
    {
        get { return _enforceTimeToLive; }
        set { _enforceTimeToLive = value; }
    }

    /// <summary>
    /// Gets the number of items in the cache.
    /// </summary>
    /// <remarks>
    /// May be overridden by subclasses for cache-specific efficient implementation.
    /// </remarks>
    public virtual int Count
    {
        get
        {
            return Keys.Count;
        }
    }

    /// <summary>
    /// Gets a collection of all cache item keys.
    /// </summary>
    public abstract ICollection Keys { get; }

    /// <summary>
    /// Retrieves an item from the cache.
    /// </summary>
    /// <param name="key">
    /// Item key.
    /// </param>
    /// <returns>
    /// Item for the specified <paramref name="key"/>, or <c>null</c>.
    /// </returns>
    public abstract object Get(object key);

    /// <summary>
    /// Removes an item from the cache.
    /// </summary>
    /// <param name="key">
    /// Item key.
    /// </param>
    public abstract void Remove(object key);

    /// <summary>
    /// Removes collection of items from the cache.
    /// </summary>
    /// <param name="keys">
    /// Collection of keys to remove.
    /// </param>
    public virtual void RemoveAll(ICollection keys)
    {
        foreach (object key in keys)
        {
            Remove(key);
        }
    }

    /// <summary>
    /// Removes all items from the cache.
    /// </summary>
    public virtual void Clear()
    {
        RemoveAll(this.Keys);
    }

    /// <summary>
    /// Inserts an item into the cache.
    /// </summary>
    /// <remarks>
    /// Items inserted using this method use the default
    /// </remarks>
    /// <param name="key">
    /// Item key.
    /// </param>
    /// <param name="value">
    /// Item value.
    /// </param>
    public virtual void Insert(object key, object value)
    {
        Insert(key, value, TimeToLive);
    }

    /// <summary>
    /// Inserts an item into the cache.
    /// </summary>
    /// <remarks>
    /// If <paramref name="timeToLive"/> equals <see cref="TimeSpan.MinValue"/>,
    /// or <see cref="EnforceTimeToLive"/> is <value>true</value>, this cache
    /// instance's <see cref="TimeToLive"/> value will be applied.
    /// </remarks>
    /// <param name="key">
    /// Item key.
    /// </param>
    /// <param name="value">
    /// Item value.
    /// </param>
    /// <param name="timeToLive">
    /// Item's time-to-live (TTL).
    /// </param>
    public virtual void Insert(object key, object value, TimeSpan timeToLive)
    {
        if (_enforceTimeToLive || (timeToLive < TimeSpan.Zero))
        {
            timeToLive = _timeToLive;
        }

        DoInsert(key, value, timeToLive);
    }

    /// <summary>
    /// Actually does the cache implementation specific insert operation into the cache.
    /// </summary>
    /// <remarks>
    /// Items inserted using this method have default cache priority.
    /// </remarks>
    /// <param name="key">
    /// Item key.
    /// </param>
    /// <param name="value">
    /// Item value.
    /// </param>
    /// <param name="timeToLive">
    /// Item's time-to-live (TTL).
    /// </param>
    protected abstract void DoInsert(object key, object value, TimeSpan timeToLive);
}
